The invention relates to a measuring device with a measuring sensor of optically active material which is suitable for detecting an electrical measurement value at high-voltage potential. In conventional measuring devices of this type, polarized light is fed by means of a light-wave conductor to this material, and from this material, light with polarization changed according to the measurement value is fed to an evaluator device also by means of a further light conductor.
U.S. Pat. 3,605,013 discloses a measuring device of this type for measuring a current in a high-voltage conductor. The measuring sensor of this device is formed by a coil of a light-wave conductor and the ends of the coil constitute a light-wave conductor for feeding the polarized light to the measuring sensor as well as a further light-wave conductor for feeding the light, with the polarization changed according to the measurement value, to an evaluator device at low-voltage potential.
The known measuring device has the drawback that it requires a relatively great length because the light-wave conductor not only forms the measuring sensor, but the distance between the high-voltage and the low-voltage potentials is bridged by the light-wave conductor twice. Light-wave conductors of the required length are difficult to fabricate and are, furthermore, very expensive which, with the great length thereof, greatly affects the manufacturing costs.